Proa type sailboats are well known in the related art. A proa sailboat typically has two hulls with bows or water cutting pointed ends on each end of the hulls. The hulls are substantially symmetrical about a longitudinal transverse center line, so that the sailboat can move in either direction with equal facility. Typically, there is a larger size main hull and a smaller size outrigger hull outwardly attached from the main hull. Also, the outrigger hull is attached on the windward side of the main hull, which is the side of the main hull that the wind first passes over. A platform can cover the area between the two hulls. Also, the mast and sail are mounted on the main hull, with one corner of the essentially isosceles triangular shaped sail attached to the top of the mast. Normally, the proa sailboat does not include a boom, and the bottom edge of the sail remains essentially parallel to the water surface, for all directions of sailing. Normally the main hull includes a rudder at each end to steer or change the direction of the sailboat. During sailing, the operator normally sits over the outrigger hull or on the platform located between the main hull and the outrigger hull.
In operation, a proa can be maneuvered to sail downwind, across the wind or upwind by tacking. In sailing upwind, the procedure differs from that which is practiced by a conventional sailboat having a pointed bow and a flat stern. In a conventional sailboat, during tacking, the bow is always the leading end of the boat. Also, in a conventional sailboat, in order to sail upwind the sailboat must change directions (tack) so that the wind blows over first one side of the sailboat and then when the sailboat direction changes, the wind then blows over the other side of the boat. When the boat changes its direction, the sail and the boom swing over to the other side of the sailboat. Since the boat changes directions, and the wind comes over first one side and then over the other side of the sailboat, a conventional sailboat is designed to be symmetrical in a cross-section perpendicular to the longitudinal axis of the hull.
For a proa, in moving upwind, the wind will always blow over the same one side of the sailboat. In tacking, the sail is adjusted and the rudder is moved such that the sailboat changes directions where the leading end going forwards before a tack becomes the trailing end going backwards after the tack. The side of the sailboat that the wind passes over first is known as the windward side, and the opposite side of the sailboat is known as the leeward side. Therefore in a proa, the windward side is always the same side of the sailboat.